After three government officials in the U.S. state of Michigan were charged with criminal offenses in the city of Flint's toxic water crisis, the question is how far up the ranks of government will anyone be held accountable for the lead poisoning in the city's corrosive water pipes.

Michigan Attorney General Bill Schuette says there will be more people charged, saying, "No one is off the table."

Some Flint residents, have called for charges against Governor Rick Snyder and his resignation. Snyder has repeatedly rejected calls to quit and has apologized for the crisis, saying "bureaucrats making bad decisions failed the people of Flint."

Asked whether he did anything criminal in his handling of the crisis, Snyder, chief executive of the Gateway computer company and a venture capitalist before winning the governorship, said, "I don't really want to get into that kind of speculation. I don't believe so."

High-level state involvement extends to April 2014, when a Snyder-appointed executive who was overseeing the management of the financially troubled city approved switching the city's water supply from the large-scale Detroit water system that draws its water from Lake Huron to the Flint River that courses through the city. The switch, which lasted until last October, was aimed at saving the city several million dollars.

But during that nearly 18-month period, officials failed to use a $100-a-day chemical to prevent corrosion of the city's water pipes, and lead leached into the drinking water. Medical tests have shown numerous Flint residents with elevated lead levels in their blood stream, including at least 200 children.

Lead poisoning diminished the learning ability of young people and leaves them prone to anti-social behavior.

Flint residents complained about the color, taste and odor of the water after switching supply to the Flint River, but government officials largely discounted their initial protests. After tests showed that the water was contaminated, officials switched the water supply back to the Detroit system.

Watch: How Flint's Water Became Toxic

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Meanwhile, government agencies and charitable groups trucked thousands of bottles of water into the city to hand out to residents, along with protective filters to add to water taps in homes.

Snyder did not acknowledge the problem until late 2015 when the medical tests showed high lead levels in children.

City officials, with only modest success, have been demanding the state and national government pay millions of dollars to remove and replace Flint's aging lead water pipes. Snyder has called for state aid for Flint, although Congress has yet to agree on assistance for the city.

Officials now claim the water is safe to drink, with use of filters as a precaution. Many residents still refuse to drink or bathe in it.

Snyder visited one Flint home earlier this week and filled jugs with tap water, saying he would drink the city's water for the next month to show how safe it is.